Blues Don't Print

I've run Self-Test Diagnostic reports and Print Quality Diagnostic reports - and they report that the printhead status is "good" for both the Black/Yellow printhead and the Magenta/Cyan printhead. However, my printer isn't printing in blues (and maybe yellows). I've done the alignment process and other simple/basic repair and maintenance steps. And all cartridges have enough/a lot of ink. I've changed them out - just to make sure.